Hydrocarbon producing wells typically have a casing or liner that is cemented therein, and a production tubing that is suspended from a tubing hanger in a wellhead. An annular packer is located between the casing and the production tubing, forcing fluids from the well to flow inside the production tubing at a certain velocity to the surface. Production from a well is generally multi-phase, wherein gas, oil, water, and/or some suspended solids, such as sand, are carried from a subterranean reservoir to the earth's surface. The ratio of the gas, oil, and/or water produced determines whether the well is considered to be a gas well, oil well, or water well. The velocity of the produced fluids is determined in part by formation pressure, or bottom hole pressure (BHP).
When a well is first drilled, its BHP is at its maximum value, therefore the velocity in the production tubing is at its highest value and the maximum amount of hydrocarbon is lifted from the well. Over time, production causes a depletion of the reservoir, a drop in BHP, and a reduction of velocity in the production tubing. As production tubing velocity decreases, droplets of well fluids can “fall back” down the well. This can lead to water accumulation in the production tubing. As the water accumulation rises in the production tubing, a hydrostatic head pressure develops therein. When the hydrostatic head pressure equals the BHP, hydrocarbon flow from the reservoir ceases.
Additional production problems that are typically encountered include: (i) emulsions can form when certain ratios of the well chemistry exist; (ii) precipitate deposition of dissolved solids can occur which will restrict and/or occlude the tubing; and (iii) corrosion can occur to production tubing due to well chemistry.
Chemical technologies have been developed to mitigate or eliminate these problems. Surfactants are commonly injected to de-water wells, and other chemicals are used to counter emulsions, precipitates, and to provide corrosion protection. One method that is well known in the industry is to deploy these chemicals through spoolable tubing, commonly known as coiled tubing, or preferably small diameter capillary tubing due to its ease of transport and manipulation. One of ordinary skill in the art will immediately appreciate that any type of tubing can be employed to accomplish the same objective. For the sake of descriptive expediency, capillary tubing shall be referenced in this disclosure to describe the use of the invention, however any type of communication conduit can be utilized without departing from the spirit of the invention.
In practice, the capillary tubing is deployed inside the production tubing, and a suitable chemical is injected from the surface through the capillary tubing to a location downhole.
A common problem occurs at the wellhead where the capillary tubing emerges from the wellhead. Typically, the capillary tubing runs through the wellhead valves, into a pressure retaining packoff, thereby emerging from the wellhead. If it becomes necessary to close one of the wellhead valves, the capillary tubing is sheared off, only to later be fished out of the well. Another well known wellhead penetration method is to construct a spool (adapted to fit between wellhead flanges) that has an opening for the capillary tubing to emerge. Unfortunately, the insertion of such a spool can change the overall height of the wellhead and alter locations of flow lines.
U.S. Pat. No. 6,851,478, hereby incorporated by reference, discloses a Y-body Christmas tree for use with coiled tubing and other wellhead components which integrates components of a Christmas tree, while providing for coiled tubing access without necessarily adding to the vertical height of the unit. However, the placement of the Y-section above the lower master valve results in shearing of the capillary tubing when the lower master valve is closed. Additionally, the Y-body Christmas tree does not facilitate retrofitting an existing master valve as the Y-body Christmas tree is a replacement for an entire existing Christmas tree, and can require significant re-piping. Pedcor, Inc., in a product brochure, discloses a chemical injection adapter which provides one mechanism for inserting coil tubing through a well head, with similar drawbacks as described above.
The present invention contemplates the above problems and provides solutions to the foregoing needs.